Abu Bakr bin 'Ayyash al-Asadi أبو بكر بن عياش بن سالم الأسدي · The Book on Al-Witr

"Allah's Messenger came out to us and he said: 'Indeed Allah has assisted you with a Salat that is better for you than red camels: Al-Witr which Allah made for you between the Isha prayer till Al-Fajr has begun."

he asked Aishah about the Witr of the Prophet. She said: "He would perform Witr during all of the night; (either) its beginning, its middle, or its end. So when he died, his Witr ended, during the approachof As-Sahar."

"Allah's Messenger would perform Al-Witr with three, reciting nine Surah from the Mufassal in them, reciting three Surah in each Rak'ah with Say: "Allah is One." At the end of them."Muhammad bin Sirin said: "They would perform Al-Witr with five, with three, and with one Rak'ah, and they considered all of that to be good."